Customizing Cluster

It shows aggregate values within a certain cluster radius, so changing the radius
changes the aggregation grouping. Note that this radius is relative to the magnification on
the map, so the number of aggregations change as you zoom in and out. The cluster color
specifies the color of the circle that reports the number of items in each aggregate. At
sufficiently high magnifications, when individual data points are visible as marks, the
cluster supports click behavior.